In radio communications, multipath interference due to reflection of signal waves is a big problem; however, linear equalizers can be used in a technique to suppress multipath interference. Recently, an equalization technique for broadband single-carrier communications that blocks several transmitting signals and equalizes their time signal in a frequency domain (hereinafter, FDE: frequency-domain equalization) has been proposed in the art. In FDE, on the transmission side, a guard interval (hereafter, GI: guard interval) of known signals such as a PRBS (Pseudo Random Bit Sequence) (referred to hereinafter as a “PN series”) is added to the lead of n pieces of blocked data signal (n symbols). These GI and n pieces of data signals constitute a frame. On the reception side, after the GI is removed from the reception frame, a data block portion is converted into a frequency domain. Next, a transmission path response in a time domain is estimated utilizing the PN series and converted into a frequency domain, and the data block portion is equalized utilizing the transmission-path response in the frequency domain.
An equalizing device for an equalizing process is provided with a first frequency domain-conversion module, a transmission path response-estimation module, an equalization module, and a time domain-conversion module. Of these parts, the first frequency domain-conversion module converts a time-domain signal in which the GI has been removed from a received signal into a frequency-domain signal. The transmission path response-estimation module includes a correlation-processing module, a PN-series generation module, and a second frequency domain-conversion module. Of these parts, the correlation-processing module calculates an estimated transmission path-response value of a time domain through correlation processing of the received signal and a PN series generated in the PN series-generation module. Next, the second frequency domain-conversion module converts the estimated transmission path-response value of the time domain into an estimated transmission path-response value of a frequency domain and outputs the estimated transmission path-response value of the frequency domain to the equalization module. The equalization module equalizes the frequency-domain signal from which the GI has been removed using the estimated transmission path-response value of the frequency domain and outputs the equalized output to the time domain-conversion module. The time domain-conversion module converts the equalized signal from the equalization module into a time domain and outputs the signal into a demodulated single-carrier signal.
In contrast, in broadcast-receiving devices in each country including Japan, when analog interference signals are received, a specification (performance) to which these signals must be able to be received up to a certain value (dB) of the D/U ratio is determined in many cases.
Therefore, even in receiving devices of single-carrier transmission, etc., it is necessary to verify effective decisions and the removal of interference signals with high frequency dependency such as interference from analog TV signals.